Sealed cartridges are known, provided to be extracted under pressure, containing a substance for the preparation of a beverage chosen from ground roasted coffee, tea, instant coffee, a mixture of ground coffee and of instant coffee, a chocolate-based product or any other dehydrated edible substance, comprising a dish with a bottom and a side wall, having substantially the shape of a frustum of a cone, and a circular edge with a diameter greater than the bottom, and a cover welded to the periphery of the edge of the dish, in which the cover consists of a flexible material which is impermeable to oxygen, chosen from the group consisting of aluminium, an aluminium/plastic composite, an aluminium/plastic/paper composite, pure or multi-layer plastic, the said cartridge not comprising a filter or a weakening zone and the cover being intended to be torn only through the effect of the force of the extraction fluid when extraction starts.
The sealed cartridge described above is the subject of Patent EP 512,468, in the name of the applicant. This cartridge is extracted with the device forming the subject of Patent EP 512,470. This extraction takes place in the following manner: the cartridge is inserted into a cartridge holder and into an extraction cage. This extraction cage comprises a needle which will pierce the bottom of the dish and, when the pressure in the cartridge rises, the cover will bear on protruding and hollowed-out elements of the extraction device. When the pressure reaches a certain level, the cover reaches its rupture tension and it opens, allowing the coffee to flow into the cup. At the end of extraction, it is possible to remove the cartridge from the extraction system in order to place the next one therein. When the said cartridge is removed, there is a hole in the bottom of the dish and this hole allows residual water and coffee grounds to escape. This leakage of grounds causes a problem, because it soils part of the extraction machine.